Characteristics of the hepatic monooxygenase system of the goldfish (Carassius auratus) and its induction with beta-naphthoflavone.

Treatment of goldfish with beta-naphthoflavone (ip) resulted in induction of hepatic monooxygenase activity in a dose-dependent manner. Levels of 7-ethoxyresorufin-O-deethylase and mexacarbate NADPH-dependent oxidative metabolism as well as cytochrome(s) P-450 were increased. Other substrates which have been associated with 3-methylcholanthrene (3-MC)-type induction in mammals were unchanged as was delta-aminolevulinic acid synthetase. Enzyme activities were inhibited by carbon monoxide and piperonyl butoxide confirming their cytochrome P-450 nature. NADH was found to stimulate metabolism in a significant manner with NADPH. pH-dependent ethyl isocyanide binding characteristics were similar in control and induced preparations while mexacarbate binding to oxidized microsomes revealed a higher apparent affinity constant (Kapps) as well as greater overall binding in induced preparations. SDS-gel electrophoresis revealed an increased band with a molecular weight of approximately 56,000.